Aqueous lubricant for plactic working of metallic material and method of lubricant film processing

ABSTRACT

A waterborne lubricant, useful in the plastic working of metals, which imparts a lubricating behavior to the surface of metals in the absence of a conversion coating contains (A) water-soluble inorganic salt, (B) lubricating agent selected from molybdenum disulfide and graphite, and (C) wax wherein these components are dissolved or dispersed in water, the (B)/(A) solids weight ratio is 1.0 to 5.0, and the (C)/(A) solids weight ratio is 0.1 to 1.0. The water-soluble inorganic salt (A) can be selected from the sulfates, silicates, borates, molybdates, and tungstates. The wax (C) can be a water-dispersed natural or synthetic wax having a melting point of 70 to 150° C. A lubricating coating is formed by application to give a post-drying add-on of 0.5 to 40 g/m2. A method for using said lubricant is also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of PCT/JP01/03639. This application claims priority from International Application Number PCT/JP01/03639, published in a non-English language, having an international filing date of Apr. 26, 2001, and to JP 2000-237968 filing date Aug. 7, 2000.

FIELD OF THE INVENTION

[0002] This invention relates to a waterborne lubricant for the plastic working of metals, such as iron, steel, stainless steel, titanium, and aluminum, that imparts an excellent lubricity to the surface of the metal and that does so without the execution of a conversion treatment on the metal surface. This invention also relates to a method for using said waterborne lubricant. More particularly, this invention relates to a waterborne lubricant for the plastic working of metals that forms, by a simple procedure and without the execution of a conversion treatment, a highly lubricating coating on the surface of a metal, such as iron, steel, stainless steel, titanium, or aluminum, that will be subjected to plastic working, such as forging, wire drawing, or tube drawing. This invention also relates to a method for forming a lubricating coating on metals in which a lubricating coating is formed on a metal surface using the waterborne lubricant according to this invention.

BACKGROUND OF THE INVENTION

[0003] A lubricating coating is usually formed on the surface of a metal, such as iron, steel, or stainless steel, that will be subjected to plastic working in order to prevent the scuffing and galling that would be produced by metal-to-metal contact between the workpiece and tool. One type of lubricating coating that can be produced on the metal surface involves the physical attachment of lubricant to the metal surface. Another type involves the application of lubricant after the production of a conversion coating on the metal surface by a chemical reaction. Physical attachment of the lubricant on the metal surface provides a poorer adherence than use of the lubricant on a conversion coating elaborated on the metal surface, and as a result the former type is usually employed with light working processes. A phosphate coating or oxalate coating is produced on the metal surface when a conversion coating is used; this conversion coating functions as a carrier. A sliding lubricant is applied after the production of this conversion coating. This type, which has a two-layer structure of conversion coating (=carrier film) and lubricant, exhibits a very high resistance to galling and as a consequence has been used over a very wide range of applications in the plastics working sector for wire drawing, tube drawing, and forging. Within the realm of plastic working operations, the application of lubricant on an underlayer of a phosphate or oxalate coating is frequently used in particular in the severe working sector.

[0004] The lubricants applied on conversion coatings can also be broadly divided into two types depending on the method of application. One type involves physical attachment of the lubricant on the conversion coating, while the other type involves a reactive attachment of the lubricant on the conversion coating. The first type includes lubricants comprising an extreme-pressure agent added to a mineral, vegetable, or synthetic base oil. The first type also includes lubricants comprising a solid lubricant (e.g., graphite or molybdenum disulfide) dissolved along with a binder component in water; these lubricants are attached by drying. Since these lubricants can be simply applied by spraying or immersion, they offer the advantage of making bath management almost unnecessary. However, due to their low lubricity they are frequently used in relatively light lubricating environments. With regard to the second type, treatment is carried out with a reactive soap, such as sodium stearate, functioning as the lubricant. Reactive soaps are used as the lubricant in particular when a high lubrication performance is required. The reactive soaps have a high lubrication performance due to their reaction with the conversion coating.

[0005] The use of a reactive soap, however, requires management of the bath providing the lubricant since a chemical reaction is involved, temperature management in order to control the chemical reaction, and waste disposal and bath renewal due to bath deterioration. Reducing the amount of industrial waste has recently become a major issue in view of the goal of global environmental protection. This has created demand for a lubricant and treatment method that do not produce waste. The complexity of process and treatment bath management in the prior-art technology has also made the appearance of a simple process desirable.

[0006] In order to solve the problems identified above, Japanese Laid-Open (Unexamined or Kokai or A) Patent Application Number Sho 52-20967 (20,967/1977) discloses a “lubricant composition comprising solid lubricant, a conversion coating-forming agent, and a base of water-soluble polymer or water-based emulsion thereof”. This lubricant composition, however, does not match conversion coating treatments.

[0007] Another means for solving the problems under consideration is, for example, the invention in Japanese Laid-Open (Unexamined or Kokai or A) Patent Application Number Hei 10-8085 (8,085/1998), which is assigned to the present applicant. This invention relates to a waterborne lubricant for the cold plastic working of metals. This waterborne lubricant comprises (A) water-soluble inorganic salt; (B) solid lubricant; (C) at least one oil component selected from mineral oils, animal and vegetable fats and oils, and synthetic oils; (D) surfactant; and (E) water. The solid lubricant is present uniformly dispersed, while the oil is present uniformly emulsified. The lubricant provided by this invention is not stable in industrial applications due to the presence of the oil component in emulsion form, and this lubricant therefore does not provide a high lubricity on a stable basis.

[0008] Yet another means for solving the problems under consideration is, for example, the invention in Japanese Laid-Open (Unexamined or Kokai or A) Patent Application Number 2000-63880, which is assigned to the present applicant. This invention relates to a lubricant composition for the plastic working of metals. This lubricant composition contains (A) synthetic resin, (B) water-soluble inorganic salt, and water, wherein the solids weight ratio (B)/(A) is 0.25/1 to 9/1 and the synthetic resin is present dissolved or dispersed. The lubricant provided by this invention does not generate an acceptable lubricity on a stable basis under severe working conditions due to its use of synthetic resin as a main component.

SUMMARY OF THE INVENTION

[0009] This invention therefore seeks to solve the problems identified above for the prior art. An object of this invention is to provide a waterborne lubricant for the plastic working of metals that can be applied to a variety of metals, enables a simple treatment, and takes global environmental protection into consideration. Another object of this invention is to provide a method for forming lubricating coatings.

[0010] As a result of intensive investigations directed to solving the problems identified above, the inventors discovered that an excellent lubrication performance is developed by an aqueous solution containing water-soluble inorganic salt, lubricating agent selected from molybdenum disulfide and graphite, and wax wherein these components are blended therein in specific ratios. This invention was achieved based on this discovery. The invention was also achieved based on the discovery of an energy- and space-saving treatment method that forms a high-quality lubricating coating at a specific coating weight on metal surfaces.

[0011] More specifically, the inventive waterborne lubricant for the plastic working of metals (hereinafter referred to simply as the waterborne lubricant) characteristically contains (A) water-soluble inorganic salt, (B) at least one lubricating agent selected from molybdenum disulfide and graphite, and (C) wax, wherein these components are dissolved or dispersed in water, the (B)/(A) solids concentration ratio (as the weight ratio) is 1.0 to 5.0, and the (C)/(A) solids concentration ratio (as the weight ratio) is 0.1 to 1.0.

[0012] The water-soluble inorganic salt used in this invention is preferably at least one selection from the group consisting of sulfates, silicates, borates, molybdates, and tungstates. In a one embodiment, the inorganic salt is selected from the group consisting of sodium sulfate, potassium sulfate, potassium silicate, sodium borate potassium borate, ammonium borate, ammonium molybdate, sodium molybdate, sodium tungstate and mixtures thereof.

[0013] In one embodiment, graphite is used as the lubricating agent. In another embodiment, molybdenum disulfide is used as the lubricating agent.

[0014] The wax used in this invention is preferably a water-dispersed natural or synthetic wax having a melting point of 70 to 150° C., preferred waxes include paraffin waxes, microcrystalline waxes, petrolatum waxes, Fischer-Tropsch waxes, polyethylene waxes, polypropylene waxes, carnauba wax, and montan wax.

[0015] The invention is also directed to a nonreactive method for forming a lubricating coating useful in the plastic working of metals on a metal surface comprising applying a waterborne lubricating coating at an add-on of at least 0.5 g/m2 to a conversion coating-free metal surface and drying the waterborne lubricating coating; said waterborne lubricating coating comprising (A) a component of water-soluble inorganic salt and (B) a component of at least one lubricating agent selected from molybdenum disulfide and graphite, and (C) a component of wax wherein these components are dissolved or dispersed in water, the (B)/(A) solids concentration ratio (as the weight ratio) is 1.0 to 5.0, and the (C)/(A) solids concentration ratio (as the weight ratio) is 0.1 to 1.0.

[0016] A preferred method for forming a lubricating coating on a metal is characterized by forming a lubricating coating at an add-on of 0.5 to 40 g/m2 on the surface of a metal by bringing the cleaned metal into contact with a lubricant as described above and then drying. The metal is preferably cleaned using at least one selection from the group consisting of shotblasting, sandblasting, alkaline degreasing, and pickling. Contact with the lubricant is preferably effected after the metal has been heated to 60-100° C. It is also preferred that the waterborne lubricant has a temperature of 50-90° C.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1A shows test specimens of selected size and shape used in the backward punch test prior to forming into a cup shape.

[0018]FIG. 1B shows a sectional view of a test specimen in the punch and die according to the backward punch test as the test is being performed.

[0019]FIG. 1C shows test specimens after forming into a cup shape in the backward punch test.

[0020]FIG. 2A shows a test specimen in position on a die for the spike test.

[0021]FIG. 2B shows a test specimen during the spike test.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0022] The elements of this invention will be explained in greater detail in the following. The water-soluble inorganic salt (A) used in the inventive waterborne lubricant functions to impart hardness and strength to the lubricating coating. The selected water-soluble inorganic salt must therefore dissolve uniformly in the solution and must form a solid coating film upon drying. Water-soluble inorganic salts with such properties preferably comprise at least one selection from the group consisting of the sulfates, silicates, borates, molybdates, and tungstates. These can be exemplified by sodium sulfate, potassium sulfate, potassium silicate, sodium borate (e.g., sodium tetraborate), potassium borate (e.g., potassium tetraborate), ammonium borate (e.g., ammonium tetraborate), ammonium molybdate, sodium molybdate, and sodium tungstate. These may be used individually or as combinations of two or more selections.

[0023] The at least one lubricating agent selected from molybdenum disulfide and graphite comprising the component (B) used by this invention functions to impart lubricity. The lubricating agent used by this invention is present in dispersed form in the inventive waterborne lubricant. A known surfactant can therefore be used as necessary or desired.

[0024] The blending ratio between the lubricating agent (B) and water-soluble inorganic salt (A) is preferably (B)/(A)=1.0 to 5.0 as the solids weight ratio. This ratio more preferably is in the range of 2.0 to 4.0. The lubrication performance is undesirably diminished when this ratio is less than 1.0, while a ratio in excess of 5.0 is undesirable due to the associated decline in the bath stability of the lubricant.

[0025] The wax (C) is not particularly restricted with regard to its structure and type, but the use of a natural or synthetic wax is preferred. The wax component is added in order to enhance the sliding properties of the coating by melting upon exposure to the heat generated during the plastic working operation. The wax should therefore have a melting point of 70 to 150° C. in order to manifest its activity in the initial working period, while the wax should also be stable in aqueous solution and should not impair the strength of the coating. The wax can be exemplified by paraffin waxes, microcrystalline waxes, petrolatum waxes, Fischer-Tropsch waxes, polyethylene waxes, polypropylene waxes, carnauba wax, and montan wax. These are preferably introduced into the inventive waterborne lubricant by mixing their water-based dispersion or water-based emulsion with the other components. The wax content preferably gives a value of 0.1 to 1.0 for the ratio (C)/(A) (solids weight ratio between the wax (C) and water-soluble inorganic salt (A)). The more preferred range for this ratio is 0.2 to 0.8. There is a risk that the sliding behavior of the coating will become unacceptable when this ratio is below 0.1, while a value in excess of 1.0 risks an unsatisfactory adherence by the coating.

[0026] An oil and/or solid lubricant may also be added to the inventive waterborne lubricant as an auxiliary when the inventive waterborne lubricant will be used in severe working operations.

[0027] Nonionic surfactant, anionic surfactant, amphoteric surfactant, or cationic surfactant can be used in those cases where surfactant is required in order to disperse the above-described lubricating agent or wax. The nonionic surfactant is not critical and can be exemplified by polyoxyethylene alkyl ethers, polyoxyalkylene (ethylene and/or propylene) alkylphenyl ethers, polyoxyethylene alkyl esters originating from polyethylene glycol (or ethylene oxide) and higher fatty acid (e.g., C12-C18), and polyoxyethylene sorbitan alkyl esters originating from sorbitan, polyethylene glycol, and higher fatty acid (e.g., C12-C18). The anionic surfactant is also not critical and can be exemplified by the salts of fatty acids, sulfate ester salts, sulfonate salts, phosphate ester salts, and dithiophosphate ester salts. The amphoteric surfactant is again not critical and can be exemplified by amino acid-type and betaine-type carboxylates, sulfate ester salts, sulfonate salts, and phosphate ester salts. The cationic surfactant is also not critical and can be exemplified by the amine salts of fatty acids and by quaternary ammonium salts. These surfactants can in each case be used singly or in combinations of two or more selections.

[0028] The waterborne lubricant according to this invention can also be used as a cold plastic working lubricant (e.g., for wire drawing, tube drawing, forging, and so forth) on metal (e.g., iron, steel, stainless steel, copper, copper alloys, aluminum, aluminum alloys, titanium, titanium alloys, and so forth) already coated by a known method with a phosphate coating (zinc phosphate, manganese phosphate, iron phosphate, tin phosphate, etc.), oxalate coating (iron oxalate, etc.), cryolite, or calcium aluminate.

[0029] The shape of the metal is not critical, and one can contemplate application to the working of not only stock such as bar or block, but also shaped material (e.g., gears, shafts) after hot forging.

[0030] The inventive method for forming a lubricating coating on metals is a nonreactive method that is characterized by the formation of a lubricating coating at an add-on of 0.5 to 40 g/m2 on the surface of a metal by bringing the cleaned metal into contact with lubricant as described above and then drying. The add-on of the lubricating coating formed on the metal surface should be adjusted as appropriate for the ensuing degree of working, but is preferably in the range of 0.5 to 40 g/m2 and more preferably is in the range of 2 to 20 g/m2. The lubricity becomes unsatisfactory when this add-on is below 0.5 g/m2. While there are no problems with lubricity at above 40 g/m2, such values are undesirable because they result in clogging of the die by residues. The add-on is calculated from the surface area and the weight difference of the metal before and after treatment.

[0031] The quantity of waterborne lubricant solids (concentration) should be suitably adjusted so as to control the add-on into the above-specified range. A procedure frequently used in practical applications involves dilution of a concentrate of the lubricant and use of the resulting dilution. The water used to make the dilution is not critical, but the use of deionized water or distilled water is preferred.

[0032] The procedure for cleaning the metal when the metal is to be submitted to application of the lubricating coating preferably is at least one selection from the group consisting of shotblasting, sandblasting, alkaline degreasing, and pickling. The purpose of this cleaning step is to remove oxide scale that has grown during, for example, annealing, and to remove various other contaminants (e.g., oil).

[0033] Environmental issues have recently made it desirable to reduce wastewater treatment loads. Zero wastewater can be achieved by cleaning the metal surface by shotblasting and then using the inventive lubricant and the described treatment method.

[0034] The procedure for effecting contact between the inventive waterborne lubricant and the metal is not critical and procedures such as immersion, flow coating, and spraying can be used. The coating time is also not critical as long as the surface becomes thoroughly coated with the waterborne lubricant. The waterborne lubricant must be dried after application. While this drying can be carried out by standing at ambient temperature, it will ordinarily be best to carry out drying at 60 to 150° C. for 10 to 60 minutes.

[0035] In order to enhance the drying performance, the waterborne lubricant is preferably brought into contact with metal already heated to 60 to 100° C. Moreover, contact is preferably carried out using waterborne lubricant heated to 50 to 90° C. These tactics lead to a substantial improvement in drying performance and can even enable drying at ambient temperature as well as enabling a reduction in thermal energy losses.

[0036] The advantageous effects of this invention will be explained in greater detail through working examples of the invention and comparative examples. The following Examples are presented as specific illustrations of the claimed invention. It should be understood, however, that the invention is not limited to the specific details of the Examples.

EXAMPLES

[0037] Test Materials

[0038] Test material for the backward punch tests: This was commercial spheroidized annealed S45C. The diameter was 30 mmØ and the height was varied from 18 to 40 mm in steps of 2 mm.

[0039] Test material for the spike tests: This was commercial spheroidized annealed S45C. The diameter was 25 mmØ and the height was 30 mm.

[0040] Treatment Sequences

[0041] Sequence A

[0042] (1) degreasing: commercial degreaser (FINECLEANER 4360, registered trademark and product of Nihon Parkerizing Co., Ltd.), concentration=20 g/L, temperature=60° C., immersion for 10 minutes

[0043] (2) water rinse: tap water, 60° C., immersion for 30 seconds

[0044] (3) lubrication treatment: lubricant at 60° C., immersion for 10 seconds

[0045] (4) drying: 80° C., 3 minutes

[0046] Sequence B

[0047] (1) shotblasting: shot diameter=0.5 mm, 5 minutes

[0048] (2) water rinse: tap water, 90° C., immersion for 90 seconds

[0049] (3) lubrication treatment: lubricant at 70° C., immersion for 5 seconds

[0050] (4) drying: ambient temperature (air current), 3 minutes

[0051] Test Methods

[0052] Backward Punch Test (See FIG. 1)

[0053] A series of cylindrical test specimens of selected dimension are shown in FIG. 1A. Specimen 2 was molded with the punch 3 and die 1 of a 200-ton crank press as shown in FIG. 1B to fabricate a cup-shaped molding. A series of resulting cup-shaped moldings, resulting from the backward punch test on the series of cylindrical test specimens of FIG. 1A are shown in FIG. 1C. This molding operation left 10 mm and produced a 50% cross section reduction. The good punch depth (mm) was designated as the largest inside height of the test specimen cups at which the inner surface remained undamaged. The material submitted to the backward punch tests was commercial spheroidized annealed S45C. The test specimens had a diameter of 30 mmØ and a height that was varied from 18 to 40 mm in steps of 2 mm. The die was SKD11; the punch was HAP40; the land diameter was 21.21 mmØ; and the working rate was 30 strokes/minute.

[0054] Spike Test (See FIG. 2)

[0055] This spike test was based on Japanese Laid-Open (Unexamined or Kokai or A) Patent Application Number Hei 5-7969 (7,969/1993). In this test, a cylindrical specimen 2 is placed as shown in FIG. 2A on a die 1 that has a funnel-shaped inner surface and is placed under a load and the specimen is pressed into the die to carry out forming as shown in FIG. 2B. This results in the formation of a spike conforming to the shape of the die. The lubricity is evaluated based on the height (mm) of the resulting spike: a higher spike height is indicative of better lubricity. The material used in this test was commercial spheroidized annealed S45C. The diameter of the test specimen was 25 mmØ and its height was 30 mm.

Example 1

[0056] Treatment was carried out using sequence A and waterborne lubricant 1 as described below (1 weight % nonionic surfactant was added for dispersion).

[0057] Waterborne Lubricant 1

[0058] Water-soluble inorganic salt: sodium tetraborate

[0059] lubricating agent: molybdenum disulfide

[0060] wax: polyethylene wax

[0061] B/A solids ratio: 3.0

[0062] C/A solids ratio: 0.4

[0063] coating weight, g/m²: 15

Example 2

[0064] Treatment was carried out using sequence B and waterborne lubricant 2 as described below (1 weight % nonionic surfactant was added for dispersion).

[0065] Waterborne Lubricant 2

[0066] water-soluble inorganic salt: sodium tetraborate

[0067] lubricating agent: graphite

[0068] wax: polyethylene wax

[0069] B/A solids ratio: 2.0

[0070] C/A solids ratio: 0.8

[0071] coating weight, g/m²: 15

Example 3

[0072] Treatment was carried out using sequence A and waterborne lubricant 3 as described below (1 weight % nonionic surfactant was added for dispersion).

[0073] Waterborne Lubricant 3

[0074] water-soluble inorganic salt: sodium silicate

[0075] lubricating agent: graphite

[0076] wax: polyethylene wax

[0077] B/A solids ratio: 1.0

[0078] C/A solids ratio: 1.0

[0079] coating weight, g/m²: 15

Example 4

[0080] Treatment was carried out using sequence A and waterborne lubricant 4 as described below (1 weight % nonionic surfactant was added for dispersion).

[0081] Waterborne Lubricant 4

[0082] water-soluble inorganic salt: sodium tungstate

[0083] lubricating agent: molybdenum disulfide

[0084] wax: paraffin wax

[0085] B/A solids ratio: 4.0

[0086] C/A solids ratio: 0.1

[0087] coating weight, g/m²: 15

Example 5

[0088] Treatment was carried out using sequence B and waterborne lubricant 5 as described below (1 weight % nonionic surfactant was added for dispersion).

[0089] Waterborne Lubricant 5

[0090] water-soluble inorganic salt: potassium sulfate

[0091] lubricating agent: molybdenum disulfide

[0092] wax: paraffin wax

[0093] B/A solids ratio: 3.0

[0094] C/A solids ratio: 0.5

[0095] coating weight, g/m²: 15

Comparative Example 1

[0096] Treatment was carried out using sequence A and waterborne lubricant 6 as described below (1 weight % nonionic surfactant was added for dispersion).

[0097] Waterborne Lubricant 6

[0098] water-soluble inorganic salt: potassium sulfate

[0099] wax: paraffin wax

[0100] C/A solids ratio: 0.1

[0101] coating weight, g/m²: 10

Comparative Example 2

[0102] Treatment was carried out using sequence B and waterborne lubricant 7 as described below.

[0103] Waterborne Lubricant 7

[0104] water-soluble inorganic salt: potassium sulfate

[0105] lubricating agent: molybdenum disulfide

[0106] B/A solids ratio: 0.5

[0107] coating weight, g/m²: 15

Comparative Example 3

[0108] Treatment was carried out using the sequence C described below.

[0109] Sequence C

[0110] (1) degreasing: commercial degreaser (FINECLEANER 4360, registered trademark and product of Nihon Parkerizing Co., Ltd.), concentration=20 g/L, temperature=60° C., immersion for 10 minutes

[0111] (2) water rinse: tap water, room temperature, immersion for 30 seconds

[0112] (3) conversion treatment: commercial zinc phosphate conversion treatment agent (PALBOND 181X, registered trademark and product of Nihon Parkerizing Co., Ltd.), concentration=90 g/L, temperature=80° C., immersion for 10 minutes

[0113] (4) water rinse: tap water, room temperature, immersion for 30 seconds

[0114] (5) soap treatment: commercial reactive soap lubricant (PALUBE 235, registered trademark and product of Nihon Parkerizing Co., Ltd.), concentration=70 g/L, 80° C., immersion for 5 minutes

[0115] (6) drying: 80° C., 3 minutes

Comparative Example 4

[0116] Treatment was carried out using sequence A and waterborne lubricant 8 as described below (1 weight % nonionic surfactant was added for dispersion).

[0117] Waterborne Lubricant 8

[0118] water-soluble inorganic salt: borax, 10%

[0119] solid lubricant: calcium stearate, 10%

[0120] oil component: palm oil, 0.5%

[0121] surfactant: polyoxyethylene alkyl alcohol, 1%

[0122] remainder: water

[0123] coating weight, g/m²: 10

Comparative Example 5

[0124] Treatment was carried out using sequence A and waterborne lubricant 9 as described below (1 weight % nonionic surfactant was added for dispersion).

[0125] Waterborne Lubricant 9

[0126] water-soluble inorganic salt: sodium tetraborate

[0127] synthetic resin: urethane resin

[0128] metal salt of fatty acid: calcium stearate

[0129] water-soluble inorganic salt/synthetic resin solids ratio=2/1

[0130] calcium stearate/synthetic resin solids ratio=3/1

[0131] coating weight, g/m²: 10 TABLE 1 Results of evaluation no. of steps backward in treatment punch spike height, sequence Treatment depth, mm mm Example 1 4 coating type 60 13.2 Example 2 4 coating type 60 13.2 Example 3 4 coating type 60 13.2 Example 4 4 coating type 60 13.1 Example 5 4 coating type 60 13.1 Comp. Ex. 1 4 coating type 40 11.6 Comp. Ex. 2 4 coating type 40 11.7 Comp. Ex. 3 6 reactive type/ 56 13.0 large amounts of waste Comp. Ex. 4 4 coating type 56 12.5 Comp. Ex. 5 4 coating type 56 12.6

[0132] The test results are reported in Table 1. As is made clear from Table 1, Examples 1-5, which employed the inventive waterborne lubricant for the plastic working of metals, gave an excellent lubricity using a simple process sequence. The lubricity was poor in both Comparative Example 1 (lacked a lubricating agent (B)) and Comparative Example 2 (lacked the wax (C)). Comparative Example 3, which gave a lubricity equivalent to that provided by this invention, employed a reactive soap treatment on a phosphate coating. Comparative Example 3, however, required wastewater treatment and bath management and could not be carried out using a simple equipment set up. Comparative Example 3 also imposed a high environmental load because the reactions were accompanied by the production of wastes. A poor lubricity in the spike test was obtained in Comparative Example 4 and Comparative Example 5. Comparative Example 4 employed the invention of Japanese Laid-Open (Unexamined or Kokai or A) Patent 

We claim:
 1. A waterborne lubricant useful in the plastic working of metals, comprising: (A) a component of water-soluble inorganic salt and (B) a component of at least one lubricating agent selected from molybdenum disulfide and graphite, and (C) a component of wax wherein these components are dissolved or dispersed in water, the (B)/(A) solids concentration ratio (as the weight ratio) is 1.0 to 5.0, and the (C)/(A) solids concentration ratio (as the weight ratio) is 0.1 to 1.0.
 2. The waterborne lubricant of claim 1, wherein the water-soluble inorganic salt (A) is at least one substance selected from the group consisting of sulfates, silicates, borates, molybdates, and tungstates.
 3. The waterborne lubricant of claim 1, wherein the wax (B) is a water-dispersed natural or synthetic wax having a melting point of 70 to 150° C.
 4. The waterborne lubricant of claim 1 wherein said wax is selected from the group consisting of paraffin waxes, microcrystalline waxes, petrolatum waxes, Fischer-Tropsch waxes, polyethylene waxes, polypropylene waxes, carnauba wax, and montan wax.
 5. A method for forming a lubricating coating, comprising the steps of: a) applying a waterborne lubricant according to any one of claims 1-4 to a conversion-coating free metal surface; and b) drying said lubricant on said metal surface.
 6. The method according to claim 5, wherein the waterborne lubricant is applied in an amount that causes the formation of a 0.5-40 g/m² lubricating coating after application and drying.
 7. The method according to claim 5, further comprising a pre-treating step of shotblasting, sandblasting, alkaline degreasing, and/or pickling the metal surface prior to step a).
 8. The method according to claim 5, wherein step a) is performed on the metal surface heated to 60-100° C.
 9. The method according to claim 5, wherein the waterborne lubricant applied in step a) has a temperature of 50-90° C.
 10. A nonreactive method for forming a lubricating coating useful in the plastic working of metals on a metal surface comprising: a) applying a waterborne lubricating coating at an add-on of at least 0.5 g/m2 to a conversion coating-free metal surface and b) drying the waterborne lubricating coating; said waterborne lubricating coating comprising (A) a component of water-soluble inorganic salt and (B) a component of at least one lubricating agent selected from molybdenum disulfide and graphite, and (C) a component of wax wherein these components are dissolved or dispersed in water, the (B)/(A) solids concentration ratio (as the weight ratio) is 1.0 to 5.0, and the (C)/(A) solids concentration ratio (as the weight ratio) is 0.1 to 1.0.
 11. The method according to claim 10, further comprising a pre-treating step of shotblasting, sandblasting, alkaline degreasing, and/or pickling the metal surface prior to step a).
 12. The method according to claim 10, wherein step a) is performed on the metal surface heated to 60-100° C.
 13. The method according to claim 10, wherein the waterborne lubricant applied in step a) has a temperature of 50-90° C.
 14. A waterborne lubricant useful in the plastic working of metals, comprising: (A) a component of water-soluble inorganic salt; (B) a component of at least one lubricating agent selected from molybdenum disulfide and graphite, and (C) a component of wax having a melting point of 70 to 150° C. wherein these components are dissolved or dispersed in water, the (B)/(A) solids concentration ratio (as the weight ratio) is 1.0 to 5.0, and the (C)/(A) solids concentration ratio (as the weight ratio) is 0.1 to 1.0.
 15. The waterborne lubricant of claim 14, wherein the water-soluble inorganic salt (A) is at least one substance selected from the group consisting of sulfates, silicates, borates, molybdates, and tungstates.
 16. The waterborne lubricant of claim 15 wherein said inorganic salt is selected from the group consisting of sodium sulfate, potassium sulfate, potassium silicate, sodium borate potassium borate, ammonium borate, ammonium molybdate, sodium molybdate, sodium tungstate and mixtures thereof.
 17. The waterborne lubricant of claim 14, wherein the at least one lubricating agent is graphite.
 18. The waterborne lubricant of claim 14, wherein the at least one lubricating agent is molybdenum disulfide.
 19. The waterborne lubricant of claim 14 wherein said wax is selected from the group consisting of paraffin waxes, microcrystalline waxes, petrolatum waxes, Fischer-Tropsch waxes, polyethylene waxes, polypropylene waxes, carnauba wax, and montan wax. 